Under the National Objectives Framework, we must use measurable indicators of freshwater quality to determine the state of our water. These indicators are called attributes, and there are several we must grade, including fish, dissolved oxygen, E. coli, macroinvertebrates, periphyton and suspended fine sediment.

These attributes are graded on a band range from A, which is very good, to D or E, which is poor or very poor.

The band grades reflect numeric measurements of water quality attributes, such as the concentration (amount) of a contaminant in the water.

For example, we monitor periphyton in rivers by measuring how many milligrams of chlorophyll-a (the green pigment in plants and algae used for photosynthesis) there are per square metre. Suppose sampling results indicate there is between 50mg and 120mg of chlorophyll-a per square metre over three years of monthly monitoring. In that case, that site achieves a B grade for periphyton.

The attribute grade for E. coli is determined using multiple metrics. According to the NPS-FM 2020, we must always present the worst-performing result as the overall grade in this case.

We use attributes to assess how well our freshwater values are being looked after.

For example, we can use the amount of suspended fine sediment (the attribute) in rivers to indicate how well ecosystem health (the value) is supported. We measure suspended fine sediment by assessing visual clarity (how far away, in metres, a black target can be seen through the water).

Under the framework, some attributes must meet a New Zealand-wide minimum standard called the national bottom line. This minimum standard is the lowest grade at which we can set our water quality targets. The region's communities must improve water quality attributes that are currently worse than the national bottom line to meet or surpass it as part of a local authority's NPS-FM 2020 implementation.

For this engagement, we will discuss the "critical four" contaminants and the target states for three of the attributes they influence:

• Nitrogen (which influences periphyton growth so is captured by the periphyton attribute)
• Phosphorous (which also influences periphyton growth so is captured by the periphyton attribute)
• E. coli (the E. coli attribute)
• Sediment (the suspended fine sediment attribute).

These four contaminants occur naturally within the region’s waterways; some even play essential roles in freshwater ecosystems. However, when excess levels of the critical four enter the awa, water quality declines.

What is nitrogen?

Nitrogen is a nutrient essential for plant and animal life and is often applied to pasture and crops as fertiliser, or is excreted by cows through their urine. Nitrogen enters the awa via land run-off after heavy rain, through groundwater, and directly via wastewater and stormwater discharges. Excess levels of nutrients in the awa can cause large amounts of weeds and algae to grow, which can choke aquatic life and cause long-term damage to the health of a waterbody.

What is phosphorous?

Phosphorus is an element that attaches to soil particles and, together with nitrogen, is an essential nutrient for plant life. This nutrient enters the awa due to erosion, land runoff after heavy rain, overland flow from poorly managed effluent application, and directly via wastewater and stormwater discharges. Too much phosphorus in freshwater can cause rapid weed growth or algal blooms, which can choke aquatic life and cause long-term damage to the health of a waterbody.

What is E. coli?

E. coli (Escherichia coli) is a type of bacteria commonly found in the gut of warm-blooded animals and people. E. coli naturally occurs in freshwater and is not usually harmful at low concentrations. Elevated levels of this bacteria indicate faecal contamination of the water, which can make people sick.

What is sediment?

Sediment refers to the small bits of soil, plant and animal matter transported by water, either in suspension (supported in the water current) or deposited on the riverbed. Fine sediment can fill up the small spaces between rocks and make the habitat unsuitable for fish and macroinvertebrates to live in. It can also make the water cloudy, which obscures hazards in the awa from people and makes the water unpalatable for stock.

What is periphyton?

Periphyton is not one of the critical four contaminants. However, it is a water quality indicator which can tell us when there is too much nitrogen and phosphorous in the awa.

Periphyton is the mix of algae, fungi, and bacteria which grows on the beds of rivers, lakes and streams and turns dissolved nutrients (such as nitrogen and phosphorous) into nutritious food for invertebrates. Excess periphyton can degrade freshwater habitats, water quality (e.g. by altering dissolved oxygen and pH) and recreational enjoyment.

When there is a rapid overgrowth of algae, we know there are high levels of nutrients in the awa. By managing these nutrients, we can influence the growth of periphyton.

When we discuss “state”, we refer to the condition of our water quality at a specific time.

Throughout this engagement, we will be discussing three states of water quality:

Baseline state

The National Objectives Framework requires local authorities to identify baseline states for water quality attributes in their region. The baseline state is an area-specific standard at which local authorities must halt the decline of an attribute and maintain or improve it.

In the Horizons region, baseline states reflect the condition of an attribute in a water management sub-zone in the five years up to 7 September 2017 (the date the 2017 National Policy Statement became operative).

When an attribute's baseline state is worse than the national bottom line, the national bottom line must be considered that attribute’s minimum standard. Where the baseline state is better than the national bottom line, the baseline is the lowest grade at which we can set its target state.

As the E. coli attribute does not have a national bottom line, we must set its target state above its identified baseline state.

Current state

The current state reflects the condition of the region’s freshwater as it is now. Horizons’ scientists consider the past five years of water quality monitoring data (up to June 2022) to determine the current state of an attribute.

Horizons calculates the current state of the awa to understand if the water is suitable for various purposes, such as swimming or as a habitat for taonga (treasured) species, and how human activities might impact freshwater.

Under the framework, if the current state of an attribute is better than its baseline state or the national bottom line, then we cannot let the attribute degrade from its current state.

Click or tap here to learn more about current states in each FMU.

Target state

Now our communities have identified values, visions, and environmental outcomes for each FMU, we must set target states for the region’s water quality attributes.

A target state is a condition an attribute must be to see our desired visions and environmental outcomes become a reality.

For example, to protect and enhance the abundance and diversity of the region’s native aquatic life (the environmental outcome), we'll need to improve the grades of many water quality attributes, including suspended fine sediment. The suspended fine sediment grade in a sub-zone might be D, causing sensitive fish and aquatic insects to disappear from the awa. This outcome is not the one communities seek, so we might set the target state for suspended fine sediment at a C grade or higher. If we can achieve a C grade for suspended fine sediment, it has a lower impact on taonga species and will lead to healthier freshwater communities.

Remember, regional councils must set an attribute's target state at or above its identified baseline state, except where it is worse than the national bottom line. In these cases, we must set an attribute's target state at or above the national bottom line. When setting water quality targets, we consider the naturally occurring processes that sometimes impact the region's awa.

Click or tap here to check out our communities' draft environmental outcomes that we used to set the region's provisional water quality targets.

The water quality targets for rivers and streams in the Horizons Region have been provisionally set based on the environmental outcomes communities want to see. This approach is like the one taken in the current One Plan.

Click or tap here to read the report outlining recommendations for setting water quality targets across the region.

The report specifically outlines the reasons why certain water quality targets have been recommended for different parts of the region. For example, one recommendation in the report is to make the default target state for suspended fine sediment across the region a C grade (the national bottom line) to provide for river ecosystem health. However, the report also recommends the target state for suspended fine sediment should be the more stringent B grade where we know a river is a habitat for threatened fish species or is a regionally significant trout fishery.

We have provisionally set the target state for E. coli better than what is recommended in the report. The report has recommended baseline state as the target for E. coli across the region. We have, however, provisionally set the default target state for this attribute at a C grade because the NPS-FM 2020 considers it the minimum water quality suitable for humans to swim in. In rivers where the baseline state is better than a C grade, the target state for E. coli will be more stringent.

Explore the map below and discover the potential target states for the periphyton, E. coli and suspended fine sediment attributes in your backyard. The map represents the target states using the band grades (A, very good – D or E, poor or very poor) discussed earlier.

If you want more detail about how we have modelled the provisional water quality targets in your sub-zone and the assumptions we made, go to our technical reports page on the Oranga Wai website.